IOS網路編程：HTTP

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IOS網路編程：HTTP

HTTP定義了一種在伺服器和用戶端之間傳遞資料的途徑。

URL定義了一種唯一標示資源在網路中位置的途徑。

 

REQUESTS 和 RESPONSES：

用戶端先建立一個TCP串連，然後發送一個請求。伺服器受到請求處理後發送一個響應向用戶端傳遞資料。然後用戶端可以繼續發送請求或者關閉這個TCP串連。

HTTPS：
在TCP串連建立後，發送請求之前，需要建立一個一個SSL會話。

request方法和它們的用途

iOS的NSURLRequest和它的子類NSMutableURLRequest提供了建立HTTP請求的方法。

NSURLResponse 和 它的子類NSHTTPURLResponse 處理返回的資料。

URL：

 

Protocol包括HTTP、FTP和file。

URL編碼：

NSString *urlString = @"http://myhost.com?query=This is a question"; 
NSString *encoded = [urlString stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];

NSURL用來管理URL。

 

IOS HTTP APIS：

涉及到下面一些類：

NSURL, NSURLRequest, NSURLConnection, 和 NSURLResponse.

1、NSURL

NSURL可以定義本地檔案和網路檔案

NSURL *url = [NSURL urlWithString:@"http://www.google.com"]; 

NSData *data = [NSData dataWithContentsOfURL:url];

NSURL定義了很多訪問器：

if (url.port == nil) { 
　　NSLog(@"Port is nil");} else {　　NSLog(@"Port is not nil");}

2、NSURLRequest

建立了NSURL後，就可以用NSURLRequest建立請求了：

NSURL *url = [NSURL URLWithString: @"https://gdata.youtube.com/feeds/api/standardfeeds/top_rated"];if (url == nil) {     NSLog(@"Invalid URL"); 

　　 return;}NSURLRequest *request = [NSURLRequest requestWithURL:url]; 

if (request == nil) {　　NSLog(@"Invalid Request");    return; }

NSMutableURLRequest是NSURLRequest 的子類，提供了改變請求的屬性的方法：

NSURL *url = [NSURL [email protected]"http://server.com/postme"]; 
NSMutableURLRequest *req = [NSMutableURLRequest requestWithURL:url]; 
[req setHTTPMethod:@"POST"];[req setHTTPBody:[@"Post body" dataUsingEncoding:NSUTF8StringEncoding]];

如果你要發送一個圖片或者視頻，那麼用需要用NSInputStream，它沒有把資料全部加在到記憶體。

NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];NSInputStream *inStream = [NSInputStream inputStreamWithFileAtPath:srcFilePath];[request setHTTPBodyStream:inStream];[request setHTTPMethod:@"POST"];

 

3、NSURLConnection

提供了初始化、開始、和取消一個串連。

4、NSURLResponse

 

 

發送同步請求：

- (NSArray *) doSyncRequest:(NSString *)urlString {    // make the NSURL object from the string    NSURL *url = [NSURL URLWithString:urlString];        // Create the request object with a 30 second timeout and a cache policy to always retrieve the    // feed regardless of cachability.    NSURLRequest *request =        [NSURLRequest requestWithURL:url                         cachePolicy:NSURLRequestReloadIgnoringLocalAndRemoteCacheData                     timeoutInterval:30.0];        // Send the request and wait for a response    NSHTTPURLResponse   *response;    NSError             *error;    NSData *data = [NSURLConnection sendSynchronousRequest:request                                          returningResponse:&response                                                      error:&error];    // check for an error    if (error != nil) {        NSLog(@"Error on load = %@", [error localizedDescription]);        return nil;    }        // check the HTTP status    if ([response isKindOfClass:[NSHTTPURLResponse class]]) {        NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *)response;        if (httpResponse.statusCode != 200) {            return nil;        }        NSLog(@"Headers: %@", [httpResponse allHeaderFields]);    }        // Parse the data returned into an NSDictionary    NSDictionary *dictionary =         [XMLReader dictionaryForXMLData:data                                   error:&error];    // Dump the dictionary to the log file    NSLog(@"feed = %@", dictionary);        NSArray *entries =[self getEntriesArray:dictionary];        // return the list if items from the feed.    return entries;}

 

 

Queued Asynchronous Requests：

- (void) doQueuedRequest:(NSString *)urlString  delegate:(id)delegate {    // make the NSURL object    NSURL *url = [NSURL URLWithString:urlString];        // create the request object with a no cache policy and a 30 second timeout.    NSURLRequest *request = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestReloadIgnoringLocalAndRemoteCacheData timeoutInterval:30.0];        // If the queue doesn‘t exist, create one.    if (queue == nil) {        queue = [[NSOperationQueue alloc] init];    }        // send the request and specify the code to execute when the request completes or fails.    [NSURLConnection sendAsynchronousRequest:request                                        queue:queue                            completionHandler:^(NSURLResponse *response,                                                NSData *data,                                                NSError *error) {                                           if (error != nil) {               NSLog(@"Error on load = %@", [error localizedDescription]);            } else {                                // check the HTTP status                if ([response isKindOfClass:[NSHTTPURLResponse class]]) {                    NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *)response;                    if (httpResponse.statusCode != 200) {                        return;                    }                    NSLog(@"Headers: %@", [httpResponse allHeaderFields]);                }                                               // parse the results and make a dictionary                NSDictionary *dictionary =                    [XMLReader dictionaryForXMLData:data                                              error:&error];                NSLog(@"feed = %@", dictionary);                // get the dictionary entries.                NSArray *entries =[self getEntriesArray:dictionary];                // call the delegate                if ([delegate respondsToSelector:@selector(setVideos:)]) {                    [delegate performSelectorOnMainThread:@selector(setVideos:)                                                withObject:entries                                             waitUntilDone:YES];                }            }    }];}

 

Asynchronous Requests：

#import <Foundation/Foundation.h>#define kDownloadComplete   @"downloadComplete"@class DownloadProgressView;@interface AsyncDownloader : NSObject <NSURLConnectionDelegate> {    // The number of bytes that need to be downloaded    long long   downloadSize;    // the total amount downloaded thus far    long long   totalDownloaded;}// A reference to the progress view to show the user how things are progressing@property (assign) DownloadProgressView *progressView;// The target MP4 file@property (strong) NSString *targetFile;// The original URL to download.  Due to redirects the actual content may come from another URL@property (strong) NSString *srcURL;// The open file to which the content is written@property (strong) NSFileHandle *outputHandle;// The name of the temp file to which the content is streamed. This file is moved to the target file when// the download is complete@property (strong) NSString *tempFile;@property (strong) NSURLConnection *conn;// instructs the class to start the download.- (void) start;@end

////  AsyncDownloader.m//  VideoDownloader////  Created by Jack Cox on 4/7/12.//   //#import "AsyncDownloader.h"#import "DownloadProgressView.h"@implementation AsyncDownloader@synthesize targetFile;@synthesize srcURL;@synthesize outputHandle;@synthesize tempFile;@synthesize progressView;@synthesize conn;- (void) start {    NSLog(@"Starting to download %@", srcURL);        // create the URL    NSURL *url = [NSURL URLWithString:srcURL];        // Create the request    NSURLRequest *request = [NSURLRequest requestWithURL:url];        // create the connection with the target request and this class as the delegate    self.conn =          [NSURLConnection connectionWithRequest:request                                        delegate:self];        // start the connection    [self.conn start];}/** * Creates a UUID to use as the temporary file name during the download */- (NSString *)createUUID{    CFUUIDRef uuidRef = CFUUIDCreate(NULL);    CFStringRef uuidStringRef = CFUUIDCreateString(NULL, uuidRef);    CFRelease(uuidRef);    NSString *uuid = [NSString stringWithString:(__bridge NSString *)                      uuidStringRef];    CFRelease(uuidStringRef);    return uuid;}#pragma mark NSURLConnectionDelegate methods/** * This delegate method is called when the NSURLConnection gets a 300 series response that indicates * that the request needs to be redirected.  It is implemented here to display any redirects that might * occur. This method is optional.  If omitted the client will follow all redirects. **/- (NSURLRequest *)connection:(NSURLConnection *)connection              willSendRequest:(NSURLRequest *)request             redirectResponse:(NSURLResponse *)redirectResponse {        // Dump debugging information    NSLog(@"Redirect request for %@ redirecting to %@", srcURL, request.URL);    NSLog(@"All headers = %@",           [(NSHTTPURLResponse*) redirectResponse allHeaderFields]);        // Follow the redirect    return request;}/** * This delegate method is called when the NSURLConnection connects to the server.  It contains the  * NSURLResponse object with the headers returned by the server.  This method may be called multiple times. * Therefore, it is important to reset the data on each call.  Do not assume that it is the first call * of this method. **/- (void) connection:(NSURLConnection *)connection  didReceiveResponse:(NSURLResponse *)response {    NSLog(@"Received response from request to url %@", srcURL);        NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *)response;    NSLog(@"All headers = %@", [httpResponse allHeaderFields]);        if (httpResponse.statusCode != 200) {// something went wrong, abort the whole thing        // reset the download counts        if (downloadSize != 0L) {            [progressView addAmountToDownload:-downloadSize];            [progressView addAmountDownloaded:-totalDownloaded];        }        [connection cancel];        return;    }            NSFileManager *fm = [NSFileManager defaultManager];        // If we have a temp file already, close it and delete it    if (self.tempFile != nil) {        [self.outputHandle closeFile];                NSError *error;        [fm removeItemAtPath:self.tempFile error:&error];    }    // remove any pre-existing target file    NSError *error;    [fm removeItemAtPath:targetFile error:&error];        // get the temporary directory name and make a temp file name    NSString *tempDir = NSTemporaryDirectory();    self.tempFile = [tempDir stringByAppendingPathComponent:[self createUUID]];    NSLog(@"Writing content to %@", self.tempFile);        // create and open the temporary file    [fm createFileAtPath:self.tempFile contents:nil attributes:nil];    self.outputHandle = [NSFileHandle fileHandleForWritingAtPath:self.tempFile];        // prime the download progress view    NSString *contentLengthString = [[httpResponse allHeaderFields] objectForKey:@"Content-length"];    // reset the download counts    if (downloadSize != 0L) {        [progressView addAmountToDownload:-downloadSize];        [progressView addAmountDownloaded:-totalDownloaded];    }    downloadSize = [contentLengthString longLongValue];    totalDownloaded = 0L;        [progressView addAmountToDownload:downloadSize];}/** * This delegate method is called for each chunk of data received from the server.  The chunk size * is dependent on the network type and the server configuration.   */- (void)connection:(NSURLConnection *)connection     didReceiveData:(NSData *)data {    // figure out how many bytes in this chunk    totalDownloaded+=[data length];        // Uncomment if you want a packet by packet log of the bytes received.      NSLog(@"Received %lld of %lld (%f%%) bytes of data for URL %@",           totalDownloaded,           downloadSize,           ((double)totalDownloaded/(double)downloadSize)*100.0,          srcURL);        // inform the progress view that data is downloaded    [progressView addAmountDownloaded:[data length]];        // save the bytes received    [self.outputHandle writeData:data];}/** * This delegate methodis called if the connection cannot be established to the server.   * The error object will have a description of the error **/- (void)connection:(NSURLConnection *)connection   didFailWithError:(NSError *)error {    NSLog(@"Load failed with error %@",           [error localizedDescription]);        NSFileManager *fm = [NSFileManager defaultManager];        // If we have a temp file already, close it and delete it    if (self.tempFile != nil) {        [self.outputHandle closeFile];                NSError *error;        [fm removeItemAtPath:self.tempFile error:&error];    }        // reset the progress view    if (downloadSize != 0L) {        [progressView addAmountToDownload:-downloadSize];        [progressView addAmountDownloaded:-totalDownloaded];    }}/** * This delegate method is called when the data load is complete.  The delegate will be released  * following this call **/- (void)connectionDidFinishLoading:(NSURLConnection *)connection {    // close the file    [self.outputHandle closeFile];        // Move the file to the target location    NSFileManager *fm = [NSFileManager defaultManager];    NSError *error;    [fm moveItemAtPath:self.tempFile                 toPath:self.targetFile                  error:&error];        // Notify any concerned classes that the download is complete    [[NSNotificationCenter defaultCenter]      postNotificationName:kDownloadComplete      object:nil      userInfo:nil];}@end

 

IOS網路編程：HTTP